You're right. We're about to launch a mobile app and working on getting it working on browser as well.
Bitcoin is a barrier but our goal is to eventually be currency agnostic. It does enable us to do escrow properly though with 2-of-3 multisig, and it also ensures that people control their own money.
it is certainly a barrier, but if sellers recognize that sales over bitcoin has lower costs (cost of fraud) - certain items should show up on these marketplaces and people knowing about that tech will be really happy to get bargains... or so it should work :)
